1. Technical Field
The present invention relates to an ink-jet recording apparatus that alleviates at least one of contamination of recording media and ink mixing resulting from maintenance such as flushing or cleaning.
2. Related Art
An ink-jet recording apparatus generally executes flushing, for example, to prevent defective printing due to drying of nozzles of a recording head (for stabilization of menisci). This action wastes ink from the nozzles by ejection irrespective of recording control signals. The unused ink ejected from the nozzles by flushing is typically received by a capping unit that seals the nozzle surface of the recording head and is then transferred, as waste ink, to a waste ink tank provided in the ink-jet recording apparatus by a suction device (see, for example, JP-A-2009-891 (Patent Document 1)).
On the other hand, one known type of ink-jet recording apparatus equipped with a serial recording head executes flushing on the movement path of the recording head without moving the recording head to the capping unit for improved print throughput (see, for example, JP-A-2002-86762 (Patent Document 2)). For example, this apparatus includes a paper guide, for transporting recording paper, that has openings through which ejected ink is received by a liquid-receiving unit (flushing box) disposed under the paper guide.
For example, flushing is executed every predetermined period during printing to prevent clogging, with thickened ink, of nozzle orifices having fewer ink droplets ejected therefrom.
On the other hand, if the nozzles of the recording head become clogged, the ink-jet recording apparatus executes cleaning, in which the capping unit seals the nozzles of the recording head and the suction device, connected to the capping unit, forcedly discharges ink from the nozzles. The unused ink ejected from the nozzles by cleaning is received by the capping unit and is then transferred, as waste ink, to the waste ink tank provided in the ink-jet recording apparatus by the suction device (see, for example, JP-A-2008-44337 (Patent Document 3)).
The flushing box is usually disposed as close to the nozzle surface as possible. If the opening side of the flushing box is distant from the nozzle surface of the recording head, ink droplets ejected from the recording head become airborne in the form of mist under air resistance before being received by the flushing box, thus contaminating the ambient environment.
As printing has diversified recently, inks containing colorants such as pigments or hollow resin particles have been used for higher reproducibility. It is known, however, that inks containing colorants such as pigments or hollow resin particles, or high-solid-content inks, do not easily permeate a waste ink absorber, such as a porous member, disposed in the flushing box; only solvent and water permeate the absorber, with the colorant deposited on the surface of the absorber.
Therefore, a pile of colorant may be deposited in the flushing box after long-term use. This ink deposit may contact the backside of a recording medium, thus contaminating the recording medium.
On the other hand, as described above, the unused ink ejected from the nozzles by flushing may also be received by the capping unit. Connected to the capping unit is the suction device, which can apply negative pressure by suction to an inner space defined by the capping unit and the nozzle surface. The ink received by the capping unit during flushing is sucked into the waste ink tank at the timing of cleaning for forcedly discharging the ink from the recording head. A problem arises, however, in that inks containing colorants such as pigments or hollow resin particles tend to foam upon suction because they contain a large amount of component, such as surfactant, for improving colorant dispersibility. It has been revealed that the resulting foam contaminates the nozzle surface and thereby causes ink mixing.
Focusing on the phenomenon that pigment ink discharged from the capping unit into the waste ink tank through a waste ink tube foams and, as a result, is less easily absorbed by the absorber provided in the waste ink tank, the invention disclosed in Patent Document 1 improves the absorbency of the absorber by impregnating at least part of the surface of the absorber that contacts waste ink with an impregnating solution containing a defoamer.
The technique disclosed in Patent Document 1, however, is not intended to alleviate foaming inside the capping unit. A fundamental solution has therefore been demanded to contamination of the nozzle surface due to foaming.